State of the art electrical circuit designs require improved EMI and ESD suppression. To achieve this in an arrangement in which one or more electrical components are mounted external to a printed wire board or chassis and connected via a flex cable requires that the flex cable include a ground plane separate from and insulated from the conductive traces of the cable and that this ground plane be effectively connected to a grounding pad on the printed wire board.
FIG. 1 illustrates a prior art flex cable arrangement in which the component mounted to pads 12 on flex cable 10 are provided with ground only through a separate set of traces 11. This arrangement may provide ineffectual EMI/ESD shielding.
FIGS. 2 and 3 illustrate a prior art flex cable shield grounding arrangement. Flex cable 20 has conductive cable traces 24 extending between component connection points 22 and a connector region 20A which is inserted into a flex cable connector 40 mounted on printed wire board 31. FIG. 3 illustrates the structure of the flex cable and the grounding structure 21 to ground the copper shielding layer 26 to a grounding pad 32 on a printed wire board 31. A plated through hole 30 extends through the various layers of the flex cable, i.e. stiffener 28, polyamide 27, copper layer 26, polyamide 25, traces 24, and polyamide 23. The plated through hole contacts copper shielding layer 26 and, together with screw 29, provides a conductive connection to grounding pad 32. This ground arrangement may not provide sufficient EMI/ESD shielding for many flex cable applications and also requires extra steps in cable manufacture and assembly of the cable into the final product.